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Risk Estimates for Uses of Phosphogypsum

05-041-124Final

This report describes work done by PNL to review and critique the EPA background information document (BID) (EPA 1992). In addition, a re-evaluation of the “Maximum Individual Risks” (MIR) were carried out for the following exposure scenarios:

(a) home built on reclaimed road constructed with phosphogypsum (PG)

(b) the application of PG as a soil conditioner or fertilizer

(c) the use of PG in research and development laboratories

The BID also gave the calculated exposures that would occur during road construction: that scenario is reviewed here, but MIR’s are not re-evaluated.

Three issues have been addressed for each scenario reviewed:

(1) appropriateness of methodology used in the BID

(2) appropriateness of model parameters used in the BID

(3) what are the best available models and parameters to do the calculations

The review of the data and parameters, and the exposure scenarios are given in Section B.1 and B.2 respectively, and the re-evaluation MIR’s are given in Section C. Calculated doses for external gamma exposures, inhalation of PG dust, and ingestion of water and food contaminated with PG are reported in the BID. These doses were converted to lifetime risks per year of exposure and compared to the risk from exposure to radon. The reason that doses were not calculated for radon exposure in the BID is not stated.

The PNL evaluation is done using the dose factors from Federal Guidance Reports FGR-11 and FGR-12 and dose and risk factors from ICRP Publications 60, 65, 66, and 68. Risks from inhalation and ingestion are calculated using ICRP Publication 60 risk factors and the dose data in ICRP Publication 68. Risks from radon exposure are taken from ICRP Publication 65.